Abstract
The molecular conformations and dynamics of poly(L‐prolyl), poly(hydroxyl‐L‐prolyl), poly(L‐prolyl‐glycyl), poly(hydroxyl‐L‐prolyl), and poly(glycyl‐glycyl‐L‐prolyl‐glycyl), in aqueous solution, have been studied using ^13^C pulse Fourier transform nmr spectroscopy. From a measurement of the intensities of major and minor resonances in the spectra of the copolypeptides, it was determined that 15–20% of the glycyl‐prolyl and glycyl‐hydroxyprolyl peptide bonds are cis. Effective rotational correlation times (τ~eff~), obtained from measurements of spin‐lattice relaxation times (T~1~) of individual backbone and side‐chain carbons, demonstrated that backbone reorientation is approximately isotropic for the five polypeptides and is characterized by correlation times of ca. 0.3–0.6 nanoseconds as a result of rapid segmental motion. In a given polypeptide glycyl and pyrrolidine residues were found to have the same backbone correlation times, but backbone carbon τ~eff~ values did decrease as the glycyl content of the peptides increased. A semi‐quantitative analysis of C^β^, C^γ^, and C^δ^ correlation times suggests that rapid ring motion in both prolyl and hydroxyprolyl involves primarily C^γ^ and C^β^, with the prolyl ring being more mobile than the hydroxyprolyl ring.